The influence of the background interference on the escape of photons in the determination of Nickel by atomic absorption analysis for a wide range of concentrations between 10 and 90ppm in an air-acetylene flame have been investigated. Assuming Doppler, Lorentzian and Voigt line profiles for the resonance lines, the resonance escape factor of the Ni-resonance lines at 2320 and 3524Å have been calculated with and without the effect of the background, in terms of two main parameters, the optical depth in the line center and the number density of absorbing atoms in the ground state. The effect of the background interference due to the presence of the SO 2 -molecular band can cause a change in the escape factors values. The dependence of the escape factor for the Voigt distribution on the damping constant is also discussed.